Question: Andrew's grandfather's age is twelve times Andrew's age. If Andrew's grandfather was 55 years old when Andrew was born, how many years old is Andrew now?
Let $a$ be Andrew's age now and $g$ be his grandfather's age now. We are looking for the value of $a$. We can set up a system of two equations to represent the given information, as follows:

\begin{align*}
g &= 12a \\
g-a &= 55 \\
\end{align*}

In particular, the second equation represents the grandfather's age $a$ years ago, when Andrew was born. To solve for $a$, we need to eliminate $g$ from the equations above. Substituting the first equation into the second to eliminate $g$, we get that $12a-a=55$ or $a=5$. Thus, Andrew is $\boxed{5}$ years old now.